ML20033E238
| ML20033E238 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/20/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20033E236 | List: |
| References | |
| NUDOCS 9003090459 | |
| Download: ML20033E238 (3) | |
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c UNITED STATES 8
J NUCLEAR REGULATORY COMMISSION 6
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wAssiwatow, o. c. rosss
%,..... p SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION L
RELATED TO AMENDMENT NO 29 TO FACILITY 0PERATING LICENSE NPF-6C AND AMENINENT NO.10 TO FACILITY OPERATING LICENSE NPF-81 GEORGIA POWER COMPANY. ET AL.
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DOCKETS NOS. 50-424 AND 50-425 L
V0GTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2
1.0 INTRODUCTION
l By letter dated August 25, 1989, Georgia Power Company, et al. (GPC or the licensee) requested changes to the Technical Specifications (TSs) for the Vogtle Electric Generating Plant (VEGP), Units 1 and 2.
The proposed changes to the TSs would revise the rod insertion limits of Figure 3.1-3 to show the fully withdrawn position as 222 steps instead of 228 steps.
The purpose of the i
change in the insertion limit is to allow a periodic change within the range of 242 to 231 steps withdrawn, of the parked full out position of the control rods which will minimize the effects of control rod wear caused by fretting against upper internal control rod guide surfaces.
Specification 3.1.3.4 would also be revised to assure that control red drop tine seasurtments are l-made from the physical fully withdrawn position (231 steps withdrawn).
In addition, a revision to TS 5.3.2 is being proposed that would indicate that control rods may utilf ze an absorber naterial of either hafnium or silver-indium-cadmium.
The use of either type of absorber esterial was described in the VEGP Final Safety Analysis Report (FSAR) and in the NRC's Safety Evaluation Report related to the operation of VEGP.
However, Section 5.3.2 of the TSs only described hafnium since that was the only absorber saterial in use at the time ~that the VEGP Units 1 and 2 licenses were issued.
Current plans are to replace control rods with absorter material of hafnium with conttel rods that use silver-indium-cadmium, beginning at the next refueling outage which is scheduled for VEGP Unit 1 in the Spring of 1990.
2.0 EVALUATION Rod Insertion Limits The control rods operate in the withdrawn position for extended periods of tine and as a result, control rod cladding wears against the control rod guide card due to coolant flow vibration.
The point of wear is local and is determined by the withdrawn parked position. Westinghouse has reconsended to its licensees a periodic repositioning of control rods to redace this wear.
For Vogtle, the current control rod parked withdrawn position is 228 steps, while the physical limit to rod withdrawal is 231 steps. The proposed c1ange will revise the TSs to allow withdrawn parled positions between 222 and 231 steps to further minimize the wear problem and to lengthen the control rod lifetime.
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The licensee evaluated the non LOCAs (loss of coolant accidents) and LOCAs that could be affected by the proposed change in rod insertion limit.
The results show that the change in rod insertion limit (between 222 and 231 steps) will not:
increase the probability of an accident previously evaluated in the
- FSAR, increase the consequence of an accident previously evaluated in the
- FSAR, cmate the possibility of a new kind of accident, or (4) deciease the safety margin.
Both the Itcensee's evaluation and the proposed TS changes to allow for withdrawn parked positions between 222 and 231 steps are acceptable for Vogtle Units 1 and 2.
t Control Rod Material The hafnium control rods have been used recently in marty Westinghouse plants.
In late 1988, the NRC staff discovered hafnium control rod swelling and cracking problems in Wolf Creek.
Subsequent reexaniinations by Westinghouse confirned that.the swelling and cracking were caused by hydriding of the hafnium material.. In March 1989, the staff issued an NRC Information Notice No. 89-31, entitled " Swelling and Cracking of Hafnium Control Rods." The staff also reviewed Westinghouse proposed hafnium control rod examination guidelines and recomnended that these guidelines be observed by all the affected licensees using hafnium control rods.
However, a better resolution to this problem is t
the replacement of hafnium control rods with silver-indium-cadmitan (Ag-In-Cd) control rods, which are less prone to the swelling problem.
The Ag-In-Cd absorber noterial was approved previously for use in control rods.
The licensee has opted to replace all hafnium control rods with Ag-In-Cd control rods for Vogtle Units 1 and 2.
The licensee evaluated the effect of changing the control rod material from hafnium to Ag-In-Cd.
The results denenstrate that no appreciable changes were observed for rod cluster control assembly worth, shutdown margin, and rod drop time since the two absorber nattrials are neu-tronically souivalent.
Based on the NRC staff's )revious approval of the use of Ag-In-Cd absorber naterial, we cont.lude that t w licensee s proposed TS change to allow the use of Ag-In-Cd control rod saterial is acceptable for Vogtle Units 1 and 2.
3.0 ENVIRON:4EhTAL CONSIDERATION L
The amendnents involve changes in requirenents with respect to the installation f
or use of facility components located within the restricted area as defined in i
L 10 CFR Part 20 and changes in surveillance requirenents. The staff has l
determined that the anendments involve no significant increase in the amounts, and no significant change in the types, of arty eff1L;ents that may be released L
of fsite and that there is no significant increase in individual or cunulative 1
occupational radiation exposure. The Commission has previously issued a proposed finding that the anendnents involve to significant hazards considera-tion, and there has been no public comment on such finding.
Accordingly, the amendments neet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(10).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessnent need be prepared in connection with the issuance of the amendments.
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4.0 CONCLUSION
The Connission ande a proposed determination that the amendnents involve no significant hazards consideration which was pelished in the Federal Register on hovenber 15,1989 (54 FR 47602), and consulted with the StM~ Georgia.
No public comments were actived, and the State of Georgia did not have any comments.
The staff has concluded, based on the considerations discussed above, that: (1) there is nasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Connission's regulations, and the issuance of the amendnents will not be inimical to the conson defense and security or to the i
health and safety of the pe lic.
Principal Contributor:
S. L. Wu Dated: February 20, 1990 t
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